Human tooth anatomy varies externally and internally. However, there are general anatomical features and patterns which are relatively consistent, such as the general shape of teeth and the general distribution of the canals found within a tooth. The space the dental pulp occupies in the coronal portion of a tooth is known as the pulp chamber. From the coronal chamber, the pulp tissue enters each tooth root through an orifice and travels in an apical direction further into the canal space, until it exits the end of the root through the apical foramina. This apical terminus is also known as the apex. Within the apical portion of a root is housed the apical constriction. The apical constriction is the narrowest portion of the root terminus. In a properly treated root canalled tooth, the apical constriction must be gagged and properly scaled.
There are many conditions which can lead to pulpal disease. when pulpal disease is diagnosed, endodontic treatment becomes necessary. Endodontic treatment is commonly known as root canal therapy. When caries for example goes untreated, it eventually begins to communicate with the pulpal tissues and leads to inflammation of the pulp. Such inflammation is known as pulpitis. Pulpitis causes severe pain and warrants endodontic intervention. When pulpitis goes untreated, the pulp tissues become necrotic (dead) in a given tooth and its associated canal systems. The residual necrotic debris that resides in the previously occupied pulpal space begins to communicate with the bone housing the tooth. This process leads to bone destruction, also known as peri-apical pathology.
The treatment of peri-apical pathology is accomplished via root canal therapy. When root canal therapy is properly carried out, the pathology will likely heal, thus saving the tooth in question. When pulpal disease goes untreated, further complications can arise. Such complications can be abscesses or cellulitis, and can potentially spread to other portions of the human body. Although it is rare, certain complications can be fatal.
When the dental specialist is faced with a patient with a diseased pulp, endodontic therapy is initiated by isolating the tooth with a rubber dam, and gaining access to the pulp by drilling through the enamel and dentin of a given tooth and reaching the pulp chamber. The next step involves locating the orifice of each canal within the particular tooth. Then, stainless steel files or nickel titanium files are used to negotiate each orifice. Following negotiation of the orifices, the working length of each canal system is established. This three dimensional complex is cleaned and shaped using various methods. Hand files of all sorts are available, as well as rotary files to clean and shape the canals of a given tooth.
Instrumenting to the proper working length is essential for endodontic success. Most often, digital apex locators are used along with x-rays to determine the working length of each canal. Apex locators measure where the apical constriction is located for each canal. The apical constriction is the location to which canal preparation should be carried.
Following and during the cleaning and shaping phase, the canals are treated with various chemical agents to destroy any left over microorganisms (detoxify). Examples of such agents are Sodium Hypochlorite (NaOCl) and EDTA.
The next step is canal obturation, or sealing of the previously instrumented canal in the tooth. The goal of obturation is to close and seal the apical constriction, and to three dimensionally fill the canal space preceding the apical constriction. Paste fillers and silver points were used in the past, but gutta percha is the standard of care used today. Gutta percha comes in thin cones of varying colors, tapers and sizes. The upper ends of the gutta percha are usually color coded to correspond to their respective sizes. Gutta percha can be thermo softened and injected into a given canal once the apical constriction has been sealed with the master cone of gutta percha. Some examples of devices used to inject gutta percha are the Obtura-II from Obtura-Spartan Endodontics, and the Calamus units of Dentsply International. Gutta percha can also be delivered using a carrier based device. Examples are Thermafil from Dentsply International, One fill from US Endodontics, and Soft-Core from Sybron Dental Specialties. Regardless of the method used, proper sealing of the root is imperative.
Following instrumentation of a given root to a given size file as described above, the canal is detoxified. A single master cone of gutta percha is placed in each respective canal. The gutta percha selected corresponds to the size of the last file used to carry out the instrumentation phase.
In multi rooted teeth, it is not uncommon to have canals instrumented to varying sizes. it is also usual that the working depth as recorded from a reference point of the coronal aspect of a tooth will vary in respective roots. Thus, different canals in a given tooth can have different working lengths and can be instrumented to different size final files. This will necessitate filling the different canals with different sized master cones.
In general, instruments and gutta percha and paper points can be color coded to correspond to each other. Paper points are typically used to dry canals prior to obturation. Paper points are also often used to carry the sealer cement into respective canals prior to inserting the master cone of gutta percha. Typically, after the master cones of gutta percha are fitted into respective canals to provide tug back, their color coded ends are seared off. The reference point where the cutting is done enables the specialist to confirm the proper working depth. The searing off of the color coded portion of the gutta percha can lead to confusion, since now there is no way to visually determine the size of the cone.
Once the master cones are inserted, a radiograph is taken to radio-graphically inspect the relationship of the master cones to the radiographic terminus of the roots. Assuming that radiographic findings and working lengths are all proper, the master cones are removed from all the canals and set aside. Typically they are placed somewhere on the bracket tray used by the dentist. Final irrigation of the canals and re-insertion of the master cones follows.
When the cones are placed on the bracket tray, it becomes difficult to know which cone goes in which canal, because their color-coded ends are seared off and because the different diameters of the cones are difficult to determine with the naked eye. Also, it is not uncommon to accidentally touch the master cones on the bracket table with another instrument; this too can lead to confusion. Further, the master cones should avoid touching any instruments previously used in the oral cavity which may have been contaminated with saliva; saliva must be kept out of the roots so as to avoid contamination. After irrigation and drying the canals with paper points, the master cones are coated with sealer of choice and cemented to working depth. Tops of master cones are then heated, condensed and spread through either lateral or vertical condensation, the latter being preferred. Accessory points are now inserted and further condensed until a dense three dimensional fill has been achieved.
The current invention addresses and eliminates the confusion that can arise from the time the master cones are removed from the tooth to the time they are replaced back into the tooth for final sealing.